Manifold Leak, SES Light

[BoneStock95Z]

for the past two years my car has had a slight exhaust leak out of the drivers side exhaust manifold at the block when its cold. the leak always went away when the engine warmed up yet here lately the leak became more noticeable and did not stop when the car warmed up. yesterday while driving around my SES light came on and i checked all my gauges as well as stopped in at a gas station to make sure all my fluids were at the right level and that there were no leaks. there were none and every time after the car runs from either 10-60 seconds the light reappears. i thought it may have something to do with open loop mode on start-up yet it doesnt seem to have any connection to the light. the car does not go into limp mode with the light on and seems to have all the power it normally does along with the normal fuel economy.

my best bet is that the leak finally got bad enough to cause low pressures in the manifold therefore setting a code, any suggestions? thanks in advance!

[USMC]

Yeah I agree with you that the leak got bad enough to cause the SES light. Typically this will happen sinceit is essentially a leak in your exhaust and its upstream from your O2 sensors. I'm assuming that the gasket failed due to continual hot exhaust burning it. This ssme thing happened to me although you're fortunate in that its on the driver side for you. Just replace and drive on.

[shoebox]

Scanning it is the only way you are going to find out what the light is for. BTW, why don't you find where the exhaust leak is and fix it?

[BoneStock95Z]

i scanned it today and it came up with a code 27 which is egr vacuum control solenoid circuit. the scanner says EGR electrical fault. now i did away with the egr on my car by blocking it at the manifolds, im guessing this is what caused the problem. I did try to fix the exhaust leak by tightening the loose exhaust manifold bolts and it seemed to help for a bit. i guess ill do that again just to see if it helps anything. thats the easiest thing for me to do at the moment anyway. im just wondering what this fault means exactly? and im glad to have guys like you all on here to help, its much appreciated.

[shoebox]

If you don't have the EGR solenoid on the car, you will get a trouble code, 'cause the computer can't see it.

[BoneStock95Z]

yeah and for some reason when the ses light comes on so do both of my fans, any insight to this? code 27 is the only one stored in the pcm. ill go tighten the manifold bolts to see if that helps the leak any at all.

[steveo]

any code that's set, if it might affect engine performance in a negative way will turn the fans on full time, and might force you into open loop (ignoring o2 sensors etc) or speed density (ignoring the maf)

you can fake out the solenoid with a resistor, or just hang the old solenoid in place until you get it tuned

once in a while it'll check for the presense of the actual EGR by checking vacuum when it's supposed to open.. you cant fake that one, and you'll find once you fake a solenoid, you'll still get a different EGR code once in a while. that will require tuning to get rid of...

fyi it would take a HUGE leak to trigger a check engine light (which would be a lean code), but it doesnt take a very big leak to effect mixture on that bank and make it run rough...

[BoneStock95Z]

while looking up codes i looked at operating data. the computer went into closed loop, it said both the fans were on which they were and the only thing i saw in operational data that seemed strange was the spark advance that peaked at 43 degrees which i dont know if this is normal. the knock sensor showed 98 once and on the next run it showed 198. i tightened the back manifold bolt and it was already stripped out. we put a slightly smaller washer on and tightened it until it caught new threads and tightened down correctly. it still had the leak which i think is coming from the end of the manifold at the stock y pipe. ill update again when i look at it tomorrow to confirm my suspicions. also the manifold numbers were between the high 400's and peaked around the mid 800's. im also not sure if this is normal as i haven't ever used tuning software.

i was planning on taking the car to rockingham saturday but luckily they called off the race because of the weather and it will be rescheduled next weekend, this buys me an extra week to sort everything out.